Sample Zone file

@ IN SOA NS.Opus1.COM. hostmaster.Opus1.COM. (

1998102601 ; serial number

43200 ; refresh 2x per day

7200 ; retry every 2 hour

2592000 ; expire after 1 month

86400 ; TTL is 24 hours

)

IN MX 10 Cello.Opus1.COM.

IN MX 10 Viola.Opus1.COM.

IN MX 15 Tennis.Opus1.COM.

IN NS ns.Opus1.COM.

IN NS Arizona.EDU.

IN A 192.245.12.8

IN A 192.245.12.7

IN HINFO "DEC-VAXCLUSTER" "OPENVMS"

;

WWW CNAME Cello.Opus1.COM.

News IN A 192.245.12.8

Tennis IN TXT "Game, set and match"

IN A 192.245.12.2 ; 100 Mbps line

IN HINFO "DEC-VAXSTATION" "OPENVMS"

IN MX 10 Mail.Opus1.COM.

IN MX 20 Mail.TheRiver.COM.

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Serial number
usually date, revision of last change

must be of increasing value for secondary to recognize the file has been modified
one of the most common problems in DNS is not properly updating this field for changes to propagate

Refresh
Time in seconds for the secondary to contact the primary to compare serial number in SOA record

Retry
Time in seconds for the secondary to retry contacting primary if the primary did not respond at refresh minutes

Expire
How long the secondary should continue to answer queries for the zone if it loses contact with the primary

Minimum TTL
The time in seconds that a nameserver can cache a resource record for use in queries before needing to contact one of the authoritative nameservers